Reconfigurable DP-16QAM/QPSK transponders for the transmission of coherent 200 Gb/s carriers in a flexgrid super-channel arrangement

The next generation of Dense Wavelength Division Multiplexing (DWDM) networks are likely to use Flexgrid arrangement, providing operators with additional flexibility when assigning spectrum compared to traditional DWDM networks using the 50 GHz ITU grid. Flexgrid breaks the spectrum up into small (typically 12.5 GHz) slots, but its key feature is that contiguous slots can be joined together to form arbitrary sized blocks of spectrum. This additional flexibility will allow faster transponders that utilize high spectral efficiency modulation techniques, like multi-level m-QAM schemes. From the use of these new spectrum efficient modulation formats and finer control over spectrum allocations, a key benefit that Flexgrid offers to the network operators is that their DWDM networks can carry more traffic with optimized spectral efficiency. High speed technology became essential for realizing greater network capacity and enabling network operators to meet the increasing bandwidth challenges from new generation superfast devices, services and applications. Coherent technologies beyond 100G are now focusing on higher level modulation formats and multiple sub-carriers/channels, using super-channels to achieve Terabit transmission.